The invention relates to a film printing method in which the transfer film, comprised of a support film and a transfer layer adhering to the transport film via a separating layer, is applied under pressure to a substrate to be provided with a print design and after removal of the transfer film the transfer layer partially or completely adheres to the substrate.
It is common to all known film printing methods that a film is partially applied under pressure to a substrate, for example, paper, cardboard, or foil in the form of sheets or endless material, and permantly fixed thereto. The transfer films are commonly in the form of foils with gold or silver appearance; however, transfer films in different colors with high gloss or mat gloss surfaces are known.
The application of the transfer film to the substrate is commonly achieved with the relief film printing method. This printing method is similar in its basic principle to the high pressure method and is in so far similar to book printing. The decisive common feature is that the printing parts of the printing mold are higher than the surrounding non-printing parts. During the printing process the print mold is indirectly heated and maintained at a uniform temperature. The printing medium that is transferred during the printing process from the printing foil to the substrate is comprised of a transfer layer in the form of a thin, multi-layer dry film which is releasably connected to a commonly transparent support film via a separating layer. The tranfer layer is comprised of two layers having a silver-colored aluminum deposit layer as well as a usually colored layer of lacquer. This double transfer layer is provided with a resin layer which upon heating has adhesive properties.
During the printing process the transfer film is guided together with the substrate to be provided with a printed design through a pressing mechanism whereby due to the pressure applied with the heated pressure mold with the elevated elements of the pressure mold predetermined locations of the transfer layer of the transfer film are removed and transferred to the substrate. Due to the heat transferred by the pressure mold the separating layer between the support film and the transfer layer is evaporated so that the transfer layer is easily removed from the support film. On the other hand, the resin layer is activated by the heat transfer from a dry state into a tacky state so that the resin layer forms an adhesive layer between the substrate and the transfer layer. As a result, at the locations predetermined by the printing mold, the transfer layer, for example, in the form of a gold-shimmering layer, is permanently applied to the substrate.
It is a disadvantage of the known film printing methods that the manufacture and positioning of the printing molds, i.e., of the stereotype plate, requires a very long preparation and adjustment time. Since the preparation and adjustment time taken up approximately half of the entire production process, the known film printing methods are, in general, very time consuming and therefor incur high production costs.
It is an object of the invention to develop a film printing method which, under consideration of the required preparation and adjusting times, makes possible substantially shorter total production times. Furthermore, a suitable film transfer device for carrying out the method should be provided.